Normal function of extra-adrenal chromaffin tissues in the young rabbit and guinea-pig

An attempt has been made to determine the relative functional activities of adrenal and extra-adrenal chromaffin tissue during the neonatal phase and up to 1 week of age using young rabbits and guinea-pigs whose main extra-adrenal abdominal para-aortic chromaffin bodies are respectively non-innervated and innervated. Amine synthesis and storage were followed by assay and autoradiography after a single intraperitoneal injection of L-[2,5,6-3H]DOPA and the findings correlated with amine content as assessed by high performance liquid chromatography and by volume of tissue. The results indicate that in the guinea-pig, in spite of differences in proportions of adrenaline and noradrenaline in the adrenal gland and para-aortic body (PAB), the loss of labelled catecholamines from the innervated PAB closely follows that from the adrenal medulla, suggesting that both participate in normal sympathoadrenal activity. By comparison, in the rabbit the PAB shows only a minimal decreased labelled amine during the first week of life during which period the amine content and concentration of the PAB doubles: the functional significance of this non-innervated extra-adrenal chromaffin tissue, which persists throughout life, has still to be determined.